Selective breeding, cloning and GM

Easy care sheep have been developed using selective breeding. Here, Dr David Scobie of AgResearch compares this traditional breeding method with the more modern cloning and genetic modification methods.

Terms to discuss: selective breeding, cloning, genetic modification

Dr David ScobieAgResearchSelective breeding is just a way of capturing a package of traits that either you fancy those traits or they are economically beneficial to you. So you can just select the animals you want, the animals that have the traits that you like and breed them together, and that is selective breeding.

A trait is just a characteristic that an animal expresses. So we might have a simple example is the horns, so some sheep have horns and some sheep don't have horns, and that is a trait that is expressed in sheep.

The first time I came across a Finnish Landrace sheep and spotted it had a short tail, I thought that would be a useful trait, and then we found some scientific literature that told us there were animals that had barer backsides, and we thought if we put those two things together, we are going to achieve what a lot of people try to achieve by docking and crutching. We would permanently genetically modify those animals so that they had a short tail and a bare backside, and we wouldn't have to keep doing that year after year.

So then we found the Finnish Landrace sheep, and then we searched until we found some sheep of a variety of breeds that had bare backsides, and we just crossed the 2 together. Some time later, we came across sheep with bare bellies and we harnessed those.

If we talk about the technology of cloning, if we had an animal that we perceived was ideal, theoretically with cloning, we could take that animal and reproduce lots and lots of them. With the traits we are talking about and the sheep we are talking about, we don't have that yet, so there is no point using cloning.

With genetic modification, it’s incredibly expensive, and you use it for bringing in traits that you are working on, whether it’s a fungus or a plant or an animal, you want to put that trait into that gene pool. In sheep, we are lucky. We have all the traits we want to work with in the sheep genome, so we don't have to bring in anything crazy from an outside gene pool. We just find the animals that have the traits we like the look of, and then we combine them together and selectively breed. It’s a lot cheaper and it has been a lot faster.